These high-performance filters are very useful: they capture 90% of large allergens like mould spores and pet dander, as well as microscopic allergens like dust, smoke, bacteria, smog, and particles that carry viruses. They remove them from the air passing through the filter. It's designed to last up to 3 months. It even meets the American Lung Association Health House Indoor Air Quality Guidelines. It's made of filtering material that won't support the growth of mould, bacteria, fungi, or mildew if used normally and as indicated. Moreover, no unnecessary antimicrobial chemicals added.